Coordinates and Equations
The coordinates for the vertices of a square centered at the origin and with side length 2 are (±1, ±1), while the interior of the same consists of all points (xi, yi) with −1 < xi < 1 and −1 < yi < 1.
The equation
describes a square of side 2, centered at the origin. This equation means "x2 or y2, whichever is larger, equals 1." The circumradius of this square (the radius of a circle drawn through the square's vertices) is half the square's diagonal, and equals . Then the circumcircle has the equation
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